1. Technical Field
The invention relates to an arrangement for transmitting, radiating and receiving high-frequency signals, comprising a system connected to a transmitting and receiving device and comprising at least one high-frequency element capable of guiding electromagnetic waves and a first signal cable extending parallel to the high-frequency element, wherein the signal cable is coupled to the high-frequency element at spaced apart coupling points in a manner suitable for carrying the high-frequency signals (Proceedings of the 1st International Conference on Tunnel Control and Communication, Nov. 28-30, 1994, pages 181 to 192).
2. Description of the Prior Art
Arrangements of this type are used, for example, with mobile telephone systems where an information link is desired between a stationary station and a mobile xe2x80x9cstationxe2x80x9d. The arrangement is particularly suited, for example, for tunnel sections in which conventional wireless radio transmission is not possible at all or only with severe limitations. A xe2x80x9chigh frequency elementxe2x80x9d employed in such arrangements is, for example, a radiating high frequency cable, hereinafter referred to as xe2x80x9cRHF cablexe2x80x9d. The RHF cable can be formed as a single piece, but can also be subdivided into segments. The high frequency element can also be in the form of a so-called array antenna comprised of a number of spaced-apart directional antennae. Although in the following only the RHF cable will be described, the associated discussions and explanations are meant to also include the other embodiments.
Because of the radiating properties of a RHF cable, high frequency (HF) energy can be received by or coupled into the RHF cable at each location thereof with appropriate antennae. However, the HF signals are strongly attenuated due to the construction of the outer conductor. Therefore, intermediate amplifiers must be incorporated in the RHF cable for longer tunnel sections so that the HF signals are received error-free along the entire transmission path.
With the conventional arrangement described in the in the aforementioned publication xe2x80x9cProceedings . . . xe2x80x9d, such intermediate amplifiers are not required. The RHF cable is here subdivided into segments which are arranged next to each other in the longitudinal direction. At predetermined distances, the segments of the RHF cable are connected in pairs with the signal cable which in this case is an optical fiber cable. Electro-optical converters are here connected between the respective segments and the signal cable. In addition, amplifiers are provided at the coupling points so that the HF signals are reliably transmitted and received along the respective two connected segments of the RHF cable. This known arrangement requires a large number of individual components for the transmission path, in particular a large number of active components. Damage to the components or a malfunction of components can noticeably interrupt the signal transmission. Signal transmission is completely interrupted if the signal cable is damaged or severed or when the transmitting and receiving device malfunctions.
It is therefore an object of the invention to improve the arrangement described so that the system can operate even if the signal cable is damage.
The object is solved by the invention in:
that parallel to the high-frequency element and with a significant spatial separation to the first signal cable, there is arranged a second signal cable which is also connected to the transmitting and receiving device, and
that the two signal cables are alternatingly connected to the high-frequency element in such a way that one signal cable is connected to all even numbered coupling points and the other signal cable is connected to all odd numbered coupling points, wherein the coupling points are numbered consecutively with integer numbers, starting at the transmitting and receiving device.
With this arrangement, the information is always transmitted via the two signal cables with low loss. Information received from the transmitter is fed at the coupling points into the RHF cable with adjustable power so that HF signals with a sufficient level can always be received along the RHF cable. The range of the transmission can thereby be significantly increased without using intermediate amplifiers, even if a substantial number of coupling points exist between the RHF cable and the two signal cables along that transmission path. The same argument also applies to HF signals from a vehicle radio transceiver or a portable radio transceiver which are fed into the RHF cable.
The second signal cable which is installed with a sufficiently large spatial separation from the first signal cable, improves the reliability of the transmission path. Even if one of the signal cables is damaged or destroyed, the system continues to operate since the RHF cable stays connected to the transmission and receiving device via the other signal cable. This enhanced service reliability is accomplished in a very simple manner. Each of the two signal cables is connected sequentially only with every other coupling point. Consequently, the equipment costs and the construction of the coupling points remain the same. The only requirement is a second signal cable.
Each of the two signal cables suppliesxe2x80x94in cooperation with the associated coupling pointsxe2x80x94segments of the RHF cable in both transmission directions. Each segment of the RHF cable receives signals from two different coupling pointsxe2x80x94as long as both signal cables are operational. In the other transmission direction, signals received by the RHF cable are also transmitted to the two coupling points which form the boundary of the respective segment.
With the separation between the coupling points properly defined, the segments of the RHF cable are reliably supplied by the still functioning coupling points even if one of the signal cables malfunctions. This means that the signals intended for a segment of the RHF cable are only fed by one coupling point in such a way that the receive level is sufficiently high along the entire length of the segment. This also means that signals received by the RHF cable are transmitted by the cable with such a low loss that the signals reach the respective single coupling point with a sufficiently high level.
If the HF cable is subdivided into segments in a manner known in the art wherein the segments are consecutively arranged in the longitudinal direction, then a single coupling point is associated with each segment. It is, for example, advantageous to subdivide the HF cable to eliminate interferences. In the event of a malfunction of a signal cable or of the associated portion of the transmitting and receiving device, the segments must be automatically and reliably connected through. For example, in DE 195 03 744 A1 there are described components provided with a switch which can be controlled by a pilot signal of the transmitting and receiving device and can satisfy the aforementioned requirements.
Embodiments of the invention will be described in the subsequent description with reference to the schematic drawings.